DALLAS – Federal officials issued urgent new safety recommendations Wednesday for a Texas oil refinery where 21 tons of deadly acid were released this summer and said they’re investigating the use of the chemical at refineries nationwide.

The head of the U.S. Chemical Safety Board said the investigation continues into the July accident at Citgo’s Corpus Christi refinery that seriously injured a worker, and accidents involving hydrofluoric acid in Illinois and Pennsylvania are also being investigated. In all, about one-third of the nation’s 150 refineries use hydrofluoric acid, or HF, in the process to make high-octane gas.

“We’re looking industrywide at the HF use in refineries and the safety of HF at the 51 refineries,” CSB investigations supervisor Robert Hall said.

The United Steel Workers union and the Sierra Club have been urging a ban on the acid for months, saying it’s too dangerous to workers and people who live nearby. The highly corrosive acid can burn eyes, eat away flesh at a rapid rate and is fatal after prolonged exposure.

At the Corpus Christi plant, a control valve failed July 19 and released an HF vapor cloud. That cloud caught fire and started explosions that released the additional 21 tons of acid vapor, about 2 tons of which escaped into the sky. The injured worker got caught up in the cloud and caught fire. Winds helped carry the massive cloud into the ship channel and away from people.

The CSB was critical of Citgo’s lack of cooperation with investigators and its early reports to state regulators about how much HF escaped.

“We believe the original release was at least 100 times larger than Citgo had originally stated,” said Hall, who noted Citgo was uncooperative with regulators.

A Citgo spokesman did not return phone calls seeking comment.

The CSB recommended that Citgo upgrade its emergency water system within 30 days. The system is used to spray down and absorb HF if it escapes, but the board’s investigation found the refinery nearly ran out of water after the first day and had to start using salt water from the ship channel.

Officials also recommended third-party audits at Citgo’s refineries in Corpus Christi and near Chicago. Refineries using HF are supposed to undergo safety audits every three years, but the CSB found neither Citgo refinery has ever had one.

The Texas Commission on Environmental Quality has “significant concerns” about Citgo’s reporting, spokeswoman Andrea Morrow said, but the agency’s investigation is still pending.

The final CSB report on the Texas accident will be finished in August, but CSB Chairman John Bresland said the urgent recommendation was issued because of fear of “imminent hazard to workers or members of the community.”

“In this case, we felt like we could not wait for the final report on our investigation,” he said.

The CSB doesn’t issue citations or fines. It makes safety recommendations to plants, industry organizations, labor groups, and regulatory agencies, and Bresland said typically those recommendations are followed.